Hearing aid transducer support



March 9, 1965 J, A. VICTOREEN HEARING AID TRANSDUCER SUPPORT Filed Aug. 18, 1960 INVENTOR. JOHN A. V/C TOEEEN United States Patent 3,172,963 HEARING TRANSDUCER SUPPORT John A. Victoreen, Colorado Springs, Coin. (350 N. Maitland Ava, Maitland, rm.) Filed Aug. 18, 1960, Ser. No. 50,464 5 Claims. (Cl. 1791il7) This invention relates to hearing aids and more particularly to a means for supporting a transducer in a hear ing aid casing.

Among the problems in hearing aids, is the prevention of microphonics which is particularly diflicult in the so-called eyeglass type of hearing aids, or for that matter in any type of hearing aid, wherein two transducers are carried by the same structure and the vibrations from one are transmitted mechanically to the other. In order to obtain most realistic reception, it is desirable to place the transducer in close proximity to the ear. It is also desirable in the interest of esthetics or cosmetics, to have the larger components which include the transducers, i.e., microphone and receiver, in the temple close to the ear or in the back of the ear.

The result is that the vibrations from the receiver are transmitted through the temple structure to the microphone and self-sustained oscillations take place.

Heretofore attempts have been made to prevent this feed back by the expedient of shock mounting the elements in sponge rubber, fiibrous materials and supposedly other dampening means. The prior devices have not been completely satisfactory in the prevention of undesirable oscillations because they were functionally vibration dampeners, based on their ability to absorb viibrations, and only work because of the large areas used and fail because of the indetermined area of contact which varies with time. The effectiveness of these prior devices also depended largely on the amount and the placement of material. For instance, if it could be possible to use a large amount of material they would operate more effectively. With the advent of the so-called eyeglass hearing aid the amount of material that can be used, and still have room for the transducer, is greatly reduced because of size limitations with the result that only a limited amount of material can be used and the effectiveness is thus reduced.

The results have been, especially when dealing with such small components, that the supplying of the dampening materials in the proper size to do an efficient job is particularly difiicult. Furthermore, the type of materials have been such that with the passage of time their effectiveness at the time of installation materially deteriorates. In addition, due to manufacturing tolerances, the effectiveness varies between otherwise supposedly identical instruments. This is particularly true of the so-called foam type materials since their inital effectiveness depends upon a myriad of small points of contact which disappear in time and which provide an intermediate initial contact.

Ideally, therefore, it is desirable to provide a support which will provide identical results in the presence of dimensional deviations due to manufacturing tolerances. The present invention provides a device wherein, although the size tolerances may vary, the support, almost immediately after assembly, conforms to the variations in existing ressures due to the case, without any deleterious elfect. In other words, I have provided a support which resiliently supports the transducers and provides an attenuation of the vibrations from between the transducers and the case and still does not have its attenuation properties reduced because of initial pressure or tolerances and which does not change materially with the passage of time.

This is because at the initial stages of assembly, the

pressure, which may be larger than desired, is almost immediately reduced to a predetermined desired value which is sufiiciently large to prevent distortion of the support due to gravitational forces, i.e., the weight of the transducer, and still retain the resiliency necessary to provide effective attenuation of the vibrations.

Briefly, this is accomplished by supporting the transducer from the enclosing case (temple) with a series of projections spaced from each other and which holds the transducer in spaced relation from the case and wherein the projections are made of a material which has a plastic flow which occurs upon a predetermined amount of pressure, and after a certain amount of time, thus reducing the pressure to a certain value, i.e., the amount of pressure which is the threshold of plastic flow, but thereafter maintains a status quo of resiliency. The

material also has what is commonly termed a plastic memory, in that should the enclosed casing become larger as is very apt to occur with cases made of plastic, the support will expand or return toward its initial state. Thus, I have provided a self-adjusting feature which automatic-ally maintains the pressure and resiliency of the attenuation characteristics at the desired amount throughout the life of the instrument.

Another advantage of the invention resides in the placement of the projections at a location where the mode of vibrational motion is at a minimum.

Still other advantages of the invention, and the invention itself, will become more apparent from the following description of an embodiment thereof, which is illustrated by the accompanying drawings and forms a part of this specification.

In the drawings:

FIG. 1 is a View, on an enlarged scale, of a portion of an eyeglass hearing aid temple, with the cro-ver plates broken away to show the interior construction;

FIG. 2 is a similar view of the rcarmo st portion of the housing broken away to show the manner of support for the microphone;

FIG. 3 is a plan view of one of the support members; and

FIG. 4 is a greatly enlarged section on the line 44 of FIG. 3.

Referring now to the drawings, throughout which like parts are designated by like reference characters, and more particularly to FIG. 1, where there is illustrated, on an enlarged scale, a portion of an eyeglass hearing aid temple. The drawings illustrate a rear portion 19 which houses a transducer 11, which may be microphone, and a reduced portion 12, in the form of a neck, which passes inward of the ear, next to the head, and a forward part 13 which houses another transducer, which may be a receiver 14. The forward portion also houses the amplifier circuitry, not shown, and continues out to a hinge, connected to an eyeglass frame which are all conventional. It will be appreciated that the position of the units may be reversed.

The microphone 11, as will be appreciated, although small, is one of the larger elements of the unit. It includes an outer casing which in this instance has an oblong or rectangular configuration well known in the art. At the center, on one of the broader sides, is provided a sound pressure inlet opening 20.

In order to reduce the size and thus the cosmetic appearance of the device, it is highly desirable that the part 10 be as small as possible. Heretofore, the difliculty has been, that it had to be large in order to provide room enough for the dampenser type material which supported the microphone. Vibrations from the receiver to the case are transmitted to the microphone, which being connected by the amplifier to the receiver causes a circuit or feed back path resulting in sustained oscillations.

This puts a definite limitation on the amount of gain that could be realized. Obviously the dampener material was supposed to prevent these oscillations.

In the present invention the cavity, in which the microphone is disposed, need only be but slightly larger than the mircophone and the improved support supports the mircophone in the cavity on its four longitudinal sides. The cavity, when the cover lilo is in place is therefore of rectangular cross-section and designed to provide substantially equal spacing between the sides and edges of the microphone and the corresponding inner walls of the cavity.

As best shown in FIG. 2, the cavity is divided between the base 1% and the cover lilo, the cover being secured in place by screws, not shown, extending through the base into the cover.

The support means is made of one of the elastoplastics, which has the properties of elasticity and plasticity, of which a number of elastromers are useful, such as vinyl chloride, polybutadieue or Polyurethane, certain silicone: elastorners and in certain instances some types of rubber formulants are examples. I have found that vinyl chlo ride is particularly useful since it has the properties of the desired high elasticity, provides a plastic flow upon a certain amount of pressure and has what is irnown in the trade as a plastic memory or recover that is the ability to return to its normal shape upon the passage of time and after pressure is relieved.

A very convenient way to make the support is in the form of a band having projections or tits on one side thereof. FIG. 3 illustrates one of these bands as it comes out of the mold. Actually, it comprises a ring 23 having substantially conical projections 24. In this instance, it will be noted that the projections 24 are placed in groups of three, on diametrically opposite sides. In operation the ring is placed on the casing of the microphone by stretching-it and at the same time turning the section 90", which is automatically accomplished due to its highly resilient nature, when it is placed on the microphone, much in the same manner as a rubber band would be placed around a rectangular package. In this instance, the projections, after the band is i place, face outwardly toward the walls of the cavity.

As best shown in PEG. 4, the most desirable form of projection for a particular application where the weight of the microphone is in the nature of one gram, is substantially a cone, the sides of which havean inclined angle of 60 and the apex has a radius which is determined by the amount of weight to be supported.

At this stage, it is pointed out that the exact shape is dictated largely by the amount of weight that is to be supported. The shape of the projection should be such that it will support the article, which may be the microphone, with no or very little distortion of the projection due to the gravitational forces of the microphone before tie cover is applied. It will be apparent that although the conical form is particularly useful in thlS particular application other forms will be found to be efiective and that the projections may be semi-sphencal, frustrums of cones, or even cylindrical or rectangular.

As previously stated, the projections were in groups of three. Thus, as can be best seen in FIGS. 1 and 2, the projections are provided at the extremities of the narrow edges and adjacent the corners of the broader sides of the microphone in this particular application. This has the advantage that the device is supported, in the case of the microphone, at the points where vibrations, which would ordinarily be transmitted into the microphone, have the least effect on the microphone. In the case of the receiver, likewise, the projections would be at points where the least vibration would be transmitted from the receiver housing to the temple casing. When the points of least vibration of the unit or where the points of least transmmission of vibration into the unit can be determined exactly, such as by measurements, the projections would be disposed at these points.

Thus with the bands as shown in FIGS. 1 and 2, the projections are at the corners where they are least effective to transmit vibrations into the microphone and hold the microphone against movement in all directions transverse to the longitudinal dimensions of the transducer. As stated, in the initial stage of the assembly the points of the projections are designed so that they will bear the weight of the transducer without substantial deformation thereof. It is important to note, however, that upon assembly, due to manufacturing tolerances of the case,

, there may be, and usually is, some slight deformation of the points. These points, being highly resilient, attenuate any vibrations from the case into the microphone. it will be appreciated that with ordinary resilient materials the degree of attenuation would depend upon the compressive forces existing on the projections after assembly. That is, the more the parts are displaced, the greater the compressive forces and the greater the loss of attenuation.

The characteristics of the above recited materials provide a new mode of operation in this instance in that the material has a ilow characteristic. That is, after a certain amount of pressure has been applied, the material will start to flow. There will be no flow prior to the threshold of pressure, but immediately after the threshold has passed this ilow will start. Thus with the passage of time, in this instance relatively short and maybe a matter of a few hours, the material will flow and as it flows the pressure will decrease until the threshld pressure of flow is reached, at which time the flow ceases. Thus almost immediately the reduction in attenuation, due to pressure, is brought back to normal attenuation after the plastic flow has ceased and there is still the amount of pressure within the range from zero flow pressure to threshold of flow pressure.

Another feature of the invention resides in the fact that any changes in the size of the cavity which will cause an increase or a decrease in pressure on the projections will be accommodated by the phenomena of plastic flow. That is, should the cavity enlarge and the pressure decrease toward zero, the plastic memory of the material will immediately start the projections to return toward their initial molded shape and the pressure will then return to the threshold of flow pressure. Thus, throughout the life of the instrument that transducer is held in the cavity with a certain amount of resiliency which only varies within extremely narrow limits and therefore the vibration attenuation characteristics are maintained substantially constant for the life of the instrument. It should be pointed out that there is practically no deterioration of the substance used over many years, particularly when it is sealed in the casing.

As previously mentioned, the sound pressure inlet hole 20 is very small and disposed in the broader side. A coupling is therefore provided which performs two principal functions, first, to insure that the sound pressures are transmitted to and only through the hole 20, and second, to insure that the microphone with the hole 20 is maintained in symmetrical relation to the opening in the cas mg.

As best shown in FIG. 2, the cover is provided with an opening 30. A connector, made of the same material as the bands 23 is provided and comprises a short tube 31, the periphery of which fills the aperture 30 tightly to prevent any sound coming into contact with the case of the microphone. The base of the tube is provided with a circular flange 31a which may be, and preferably is, cemented to the side of the microphone with the center of the tube coaxial with the opening 20. The tube thus being engaged with the wall of the hole 30 holds the transducer against longitudinal movements with the ends away from contact with any obstruction in the cavity and properly centered longitudinally.

It will also be appreciated that the bands as well as the connector are extremely easy to install, thus decreasing the assembly time. Furthermore, once installed they enable disassembly at any time with a minimum of effort and without mutilating any of the parts.

At this point is should be pointed out that one of the main features of the invention resides in the recognition that the material selected is new to this application and performs in an entirely different manner than the prior art to provide both a new and an improved result and that although the use of bands as described is extremely efficient, economical and easy of installation that the concepts of the invention could be practiced and many of the advantages realized by the use of other structures than that illustrated. For instance, instead of bands, strips of the elastomer could be cemented to the transducer. In addition, it is possible that strips could be cemented to the casing and the projections engaged with the transducer.

It should be pointed out that variations in the connector 30 could be used.

The manner of support for the receiver or sound reproducing element 14 is similar to that described in connection with the microphone 11, the differences being largely due to the possible difference in shape and size. The receiver is disposed in a cavity in the portion of the temple forward of the ear at the forward end of the neck 12. The bands 23 are provided adjacent the ends having the projections 24 engaged with the wall of the cavity. As in the case described, the cavity is partly Within the base and partly within a cover 40 which, in this instance, is secured to base in a similar manner by screws, not shown.

An additional band 41 is provided in this instance having only two projections 42, the band being applied to the receiver so that it extends around the receiver longitudinally with the projections at opposite ends of the receiver. In this instance, one of the projections engages a boss 43 which receives the screw that holds the cover on. The other projection engages with an abutment 44 which is carried by the chassis board, a portion of which is shown at 45 and which likewise is secured into the casing by screws, not shown, which pass through the base of the casing and holes 46 into the cover. Thus, the unit is held against transverse and longitudinal movements in all directions. A complete isolation of the unit 14 from the casing is also provided for the sound outlet. In this case the sound outlet comprises a short tube 50 which may be metal and is integral with the unit. The outer casing of the unit is provided with an opening 51. Obviously one-half of this opening is provided in the base and the other half in the cover, and a metal coupler which comprises a base 52, having a circumferential groove 53, is slipped into position with the groove receiving the edges of the opening 51. Outwardly the coupling is provided with a nipple 54 for the reception of a tube having an ear piece, not shown.

A seal is provided and comprises a tube 56 also of vinyl chloride which tightly engages with and is telescoped on the tube 50. The outer end of the tube is provided with a circular flange 57, which is engaged with the enlarged bore 58 of the coupling 52. It will be noted that the flange 57 is larger than the bore 58 so that it is distorted by engagement with the bore and thus provides a light seal therewith. Due to the flexibility of the tube 6 56 and the flange 57, complete isolation of the receiver is provided from the casing for vibrations from the receiver and yet an effective transmission of sound pressures is relayed to the ear tube.

Having thus described the invention, in an embodiment thereof, it will be appreciated that numerous and extensive departures will be apparent to those versed in the art, without departing from the spirit or scope of the invention as defined in the appended claims.

I claim:

1. A support for supporting a transducer in a casing which surrounds the transducer, comprising a plurality of projections disposed between the transducer and the casing and spacing the transducer from the casing on opposite sides, formed from a class of materials having high elasticity, plastic flow and permanent plastic memory, and being disposed within the casing under sufficient pressure to deform projections and allow the plastic flow to decrease the pressure to the point where the threshold of deformation is reached.

2. A support as described in claim 1, wherein the material of said projections is an Elastoplast.

3. A support as described in claim 2, wherein the projections are of decreasing diameter in all transverse dimensions from their base to the point of support.

4. A hearing aid comprising a substantially rigid casing formed to provide a housing having a cavity for receiving a transducer, a transducer having a housing disposed in said casing, means to support said transducer in the casing and to isolate the transducer housing for vibration to and from the casing comprising a band of material disposed around the transducer housing and having a plurality of outwardly extending projections which extend into engagement with said first housing inner wall, said projections being formed from a class of materials having high elasticity, plastic flow and permanent plastic memory and the dimensions of the casing and the transducer being such that said projections are pressed into engagement with the casing under sufficient pressure to deform the projections and allow the plastic flow to decrease the pressure to the point where the threshold of deformation is reached.

5. A device as described in claim 4, wherein the band of material is formed as a ring with the projections disposed on one side of the ring and the ring is deformed by stretching it and rotating the cross section when it is placed over the transducer to cause the projections to be disposed on the outer side of the ring.

References Cited by the Examiner UNITED STATES PATENTS 2,578,809 12/51 Ketchum 179-10041 2,858,881 11/58 Newall et a1. 2,894,076 7/59 Posen 179-l07 3,025,200 3/62 Powers 15454 3,049,260 8/62 Stone 206-46 FOREIGN PATENTS 650,140 2/51 Great Britain.

ROBERT H. ROSE, Primary Examiner.

L. MILLER ANDRUS, STEPHEN W. CAPELLI,

Examiners. 

1. A SUPPORT FOR SUPPORTING A TRANSDUCER IN A CASING WHICH SURROUNDS THE TRANSDUCER, COMPRISING A PLURALITY OF PROJECTIONS DISPOSED BETWEEN THE TRANSDUCER AND THE CASING AND SPACING THE TRANSDUCER FROM THE CASING ON OPPOSITE SIDES, FORMED FROM A CLASS OF MATERIALS HAVING HIGH ELASTICITY, PLASTIC FLOW AND PERMANENT PLASTIC MEMORY, AND BEING DISPOSED WITHIN THE CASING UNDER SUFFICIENT PRESSURE TO DEFORM PROJECTIONS AND ALLOW THE PLASTIC FLOW TO DECREASE THE PRESSURE TO THE POINT WHERE THE THRESHOLD OF DEFORMATION IS REACHED. 